The present invention relates to a fuel injector.
German Published Patent Application No. 195 34 445 discusses a fuel injector having a piezoelectric actuator for operation of a valve needle connected to a valve closing body. The valve closing body cooperates with a sealing seat.
It is believed that a disadvantage of this injector is the relatively short stroke travel of the piezoelectric actuator, which is composed of several piezoelectric layers arranged in a stack, for the relatively large lifting forces.
Furthermore, it is believed that such a fuel injector may be implemented only as either an inward opening valve or an outward opening valve. Various requirements of such valves, however, may also necessitate outward or inward opening with a design that is otherwise the same. To this end, the working direction of the actuator must be reversed. In German Published Patent Application No. 195 00 706, this is apparently accomplished by a hydraulic reversal of direction. The hydraulic device for reversal of direction, which may be difficult to implement in the design, and the greater space that may be required by such a hydraulic device are believed to be disadvantages. Other disadvantages may include hydraulic fluid leakage losses and subsequent negative effects on the functioning and lifetime of the hydraulic device and thus the entire fuel injector.
The fuel injector according to an exemplary embodiment of the present invention, is believed to have the advantage that the working direction is reversed by purely mechanical toggle elements. Therefore, it is believed that the exemplary embodiment of the present invention may be less susceptible to malfunction, may be advantageous to manufacture and may require relatively little space.
The reversal of direction achieved by the toggle elements can be used in a variety of ways and is not limited to piezoelectric actuators.
Furthermore, it is believed that by slightly redesigning the toggle elements, the relatively short stroke produced by the piezoelectric actuator can be geared up by lengthening the lever arm, and the stroke acting on the valve needle can be increased.
It is believed that the fuel injector according to the exemplary embodiment of the present invention is also characterized by a high precision in the opening and closing times and thus also in the metered quantity of fuel, because there is no delay in the reversal of direction or in gearing up the stroke.